It is already known to use graphite for electric arc-electrodes. A solution of this type is described in DT-AS 1,154,548. The contacts or contact spuds of an electric switch, which generate an electric arc upon the switch being switched off, are made of graphite. In switches of this type, graphite contacts are particularly advantageous, if an electro-negative and fluoride-containing gas, particularly sulphurhexafluoride SF.sub.6, is employed as a means to extinguish the electric arc. The material loss of graphite contacts is considerably smaller than that of the metallic contact. This is so even if the latter consist of high grade, electric arc-resistant material, such as silver- or copper-wolframite.
Problems arise in electric power switches having graphite electrodes, since the graphite members used as electric arc-electrodes must be mechanically or electrically connected with the current-carrying contacts. Graphite members are not, however, as a rule, of adequate rigidity, and therefore do not permit the cutting of a thread for connection to a contact. In order to increase this mechanical rigidity, it has already been proposed to provide the graphite members with an electrically conducting add-on piece consisting of one or a plurality of metals at positions where a galvanic or mechanical contact with the contact spud takes place (DT-OS 2,221,630).
Another type of attachment of the graphite member to the contact spud is described in DT-OS 2,230,927. The jetshaped electric arc-electrode consisting of graphite is cold-pressed into a tube manufactured from cold-formed copper and surrounded by the latter, employing frictional contact. DT-OS 2,232,314 describes a shrink-fit or connection between the graphite member and the contact spud, which is implemented by means of a ring-shaped metallic member. In order to keep the contact resistance between the graphite member and the contact spud as small as possible, however, one has to expect the exertion of considerably high pressure on the graphite member, which is undesirable in view of the relatively small mechanical rigidity of the graphite. Accordingly, the graphite member may break or rupture during installation or operation.